If "bpy" in locals(): evals to True on first run
Following batFINGER's sage advice, I've done the following. I think I get the from make_Shaders.make_Shaders import xxxx now. I haven't seen this syntax exactly anywhere, but it works an absolute treat. My actual statement is:

from make_shaders.make_shaders import buildShader
from make_shaders.figure_defs import matZones


'buildShader' and 'matZones' both being classes. This approach works perfectly, and is an excellent solution to managing multi-file modules. Incidentally, I took out the add to syspath stuff as well. Thank you, batFINGER. Wish you did a correspondence course... :)